1. Field of the Invention
The present invention relates generally to hydraulic fluid reservoirs and, more particularly, to a hydraulic fluid reservoir including a cooling system.
2. Description of the Prior Art
Aircraft engines require lubrication. Aircraft turbine engine lubricating systems generally comprise a hydraulic circuit including a pump drawing oil from an oil tank to provide lubrication to engine components, such as bearings, via distribution lines, and return lines to return the oil back into the tank. A separate oil cooler, such as an air-cooled oil cooler or a fuel-oil heat exchanger, is typically connected to the return line in series with the oil tank to cool the lubricating oil that has been pumped therefrom. Such a separate oil cooler adds to the cost and weight of the engine lubricating system.
U.S. Pat. No. 4,947,963 issued on Aug. 14, 1990 to Aho discloses a vented oil supply reservoir for aircraft comprising a substantially cylindrical swirl vessel enclosed within an oil tank for permitting venting and adequate supply of oil at all altitudes. Return oil from exterior equipment is tangentially introduced into the swirl vessel so as to create a forced vortex in the vessel. A drain is provided at the bottom of the vessel to permit excess oil to drain into the interior of the oil tank about the swirl vessel. This arrangement requires a separate oil cooler external to the oil tank to cool the lubricating oil that has been pumped therefrom.
U.S. Pat. No. 5,718,281 issued on Feb. 17, 1998 to Bartalone et al. discloses a combined cooler, reservoir and filter for an automobile power steering system. The reservoir comprises a frusto-conical sidewall made of heat conductive material and having cooling fins extending outwardly therefrom. The oil is introduced into the interior of the reservoir via an inlet provided at a bottom end thereof and is caused to flow axially upwardly before being recirculated axially downwardly along the inner surface of the frusto-conical side wall. Air is circulated over the cooling fins to remove heat from the power steering fluid contacting the interior surface of the frusto-conical wall.
Although, the combined cooler, reservoir and filter disclosed in the above-mentioned patent performs satisfactorily when used in an automobile power steering system, it has been found that there is a need for a new convectively-cooled fluid reservoir offering increased cooling capacity.
It is therefore an aim of the present invention to provide a new hydraulic fluid reservoir wherein the hydraulic fluid is cooled within the reservoir, thereby dispensing with the need for a separate hydraulic fluid cooler.
It is also an aim of the present invention to increase the heat dissipation rate of a hydraulic fluid reservoir.
It is a further aim of the present invention to provide a new method of cooling a hydraulic fluid within a reservoir.
Therefore, in accordance with the present invention, there is provided a combined cooler and oil tank system, comprising an oil tank having a tank cavity, a vortex chamber integrated to said oil tank, said vortex chamber having a side wall, an inlet at an upper end portion of said vortex chamber for directing incoming oil, under pressure, into said vortex chamber in a generally tangential fashion and causing said incoming oil to centrifugally contact an inner surface of said side wall while the oil swirls down to a lower end portion of said vortex chamber; a heat exchange promoting structure on an outer surface of said side wall of said vortex chamber for promoting heat transfer from the oil to a cooling fluid flowing over said heat exchange promoting structure as the oil swirls down along said inner surface, and an outlet at said lower end portion of said vortex chamber for directing cooled oil into said tank cavity.
In accordance with a further general aspect of the present invention, there is provided a convectively-cooled hydraulic fluid tank apparatus comprising a hydraulic fluid tank, a fluid cooler incorporated into said hydraulic fluid tank, said fluid cooler including a vortex chamber having a wall at least partly made of a heat conductive material, said wall having inner and outer surfaces, an inlet directing incoming pressurized hydraulic fluid tangentially onto said inner surface of said wall to create a swirled flow of hydraulic fluid against said inner surface of said wall, and a heat transfer promoting structure on said outer surface of said wall.
In accordance with a further general aspect of the present invention, there is provided a method of cooling a hydraulic fluid within a tank, comprising the steps of: providing a vortex chamber within a tank, directing a hydraulic fluid to be cooled into said vortex chamber in a tangential fashion, causing said hydraulic fluid to centrifugally contact an inner surface of a wall of said vortex chamber while said hydraulic fluid flows along said inner surface, and cooling the hydraulic fluid maintained in contact with the inner surface of the wall by removing heat from the hydraulic fluid through the wall.
The term hydraulic is herein intended to characterize any fluid that is circulated through conduits usually by pressure.